Indicator for heat rays



Aug. 16,1927. R' MECHAU INDICATOR FOR HEAT RAYS 4 Filed Aug. 13. 1921 f (dw 0 Xp? .h )L g/ e; `\e c Fig.4

@mM/vtm s @M/MMM Patented ug. 16, 1927.

UNITED STATES PATENT oFFlcE.

ROBERT MECHA'U, 0F JENA, GERMANY, ASSIGNR TO THE FIRM 0F CARL ZEISS, OIF JENA, GERMANY.

INDICATOR FOR HEAT RAYS.

Application led August 13, 1921, Serial No. 492,136, and in Germany October 25, 1917.

The present invention relates to indicators for heat rays which are provided with a collective system serving for receiving the rays of heat, in the focal plane of which system a heat-sensitive device is disposed, in which changes of temperature evoke alterations in the intensity of an electric current passing through it. The invention consists in that the said indicators are equipped with a semispherical auxiliary mirror the center of curvature of which coincides with the focal point of the collective system, and the opening of which faces this system, and that the receiving surface of the heat-sensitive device is disposed outside the Voptical axis of the collective system. This manner of construction aiords the possibility of uniting a certain number of rays, the existence of which is to be proved, on a receiving surface of the heat-sensitive device which need only be half the size of that hitherto necessary for receiving the same number of rays, in virtue of the fact that the new arrangement permits of a radiation of the heatsensitive device from two sides, i. e. from the front and from the back. The heatsensitive devices may thereby consist of thermo-elements, or thermo-piles, or hot wires for bolometric arrangements.

If besides the one heat-sensitive device other such devices of the same kind and of approximately the same size are disposed in the focal plane of the collective system, it will be recommended to have the spaces which, of course, have to be left between the individual devices so that rays which leave the collective system may reach the auxiliary mirror, equal to the width of the heat receiving parts of the devices, so as to fully utilize the rays emerging from the collective system.

The annexed drawing shows a constructional example of an a pliance according to the invention, in the ocal plane of which there are disposed two thermo-elements.

Fig. 1 is a section perpendicular to the optical axis of the collective system on line 1-1 of Fig. 2. Fig. 2 is partly a side-view,

and partly a section in the direction of the optical axis ofthe colletcive system.

The appliance is equipped with a concave mirror b, which is disposed in a casing a., and serves for collecting the rays the existence of which is to be proved. This mirror is faced by a small semi-spherical auxiliary mirror c, the optical axis X-X of which coincides with the axis of the concave mirror b. Between the two mirrors, in the focalplane of the mirror b, two thermo-elements are disposed, which consist each of an iron wire d to which a constantan plane e is soldered, the iron wire of one element being connected to a metal clip f, and the constantan plate of the other element to a metal body g, while the iron wire of the second element and the constantan plate of the first are connected to a common metal clip it, in which manner the two `elements are connected in series; besides, the metal clip fiand the metal body g are connected with each other through a galvanometer G. In this instance the surfaces of the constantan plates e having the width z', which surfaces appear in Fig. l between the iron wires d, have to be considered to be the receiving surfaces of the heat-sensitive devices. The distance apart of the two receiving surfaces is equal to the width i of these surfaces, in which manner this appliance permits of utilizing a pencil of rays having four times the width of a receiving surface.

I claim:

1. In an indicator for heat rays the cornbination with a casing having an aperture therein, of a collective optical system fixed relatively to the aperture, a semispherical mirror having a smaller diameter than the said system and being fixed within the said casing, the centre of curvature of this mirror coinciding with the focal point of the said system and its openingfacing this system, and a heat sensitive device located in the said casing in the focal plane of the said system, set off from the axis of the same. i

2. In an indicator for heat rays the combination With a casing having an aperture therein, of a collective optical system fixed relatively to the aperture, a semispherical mirror having a smaller diameter than the' 5 said system and being fixed Within the said casing, the centre of curvature of this mirror coinciding with the focal point of the said system and its opening facing this sys- Maaate tem, a plurality of heat sensitive devices, all such devices being of approximately the same size and being located in the said casing in the focal plane of the said system, every two such devices having a space between them about equal to the Width of the devices.

ROBERT MECHAU. 

